Indexable inserts to be detachably mounted on tools for cutting workpieces have been known. As such indexable inserts, many cutting tips each including a substrate composed of a cemented carbide or cermet and a hard coating of ceramic formed thereon for improving wear resistance and toughness have been proposed.
In such indexable inserts, various attempts have been made to improve characteristics by changing the composition of a hard coating or differentiating the thickness of the hard coating on a flank face from that on a rake face (Japanese Unexamined Patent Application Publication No. 2001-347403 (Patent Document 1), Japanese Unexamined Patent Application Publication No. 2004-122263 (Patent Document 2), Japanese Unexamined Patent Application Publication No. 2004-122264 (Patent Document 3), and Japanese Unexamined Patent Application Publication No. 2004-216488 (Patent Document 4)).
In contrast, an attempt has recently been made to form an outermost layer of a color different from that of a lower layer in the hard coating so that the use state of an indexable insert is identified from the discoloration of the outermost layer (Japanese Unexamined Patent Application Publication No. 2002-144108 (Patent Document 5). However, this attempt has caused the problem of welding of the outermost layer used for identifying the use state and a workpiece during cutting, thereby degrading the surface state of the workpiece. However, substantially no attempt has been made to resolving the problem.
Japanese Unexamined Patent Application Publication No. 2001-347403 (Patent Document 1)
Japanese Unexamined Patent Application Publication No. 2004-122263 (Patent Document 2)
Japanese Unexamined Patent Application Publication No. 2004-122264 (Patent Document 3)
Japanese Unexamined Patent Application Publication No. 2004-216488 (Patent Document 4)
Japanese Unexamined Patent Application Publication No. 2002-144108 (Patent Document 5)